The AI has been building stupendous priest stacks lately, neglecting all the other units and then just camping one city with them. I've had multiple games where the AI has had some 50-120 (about thrice the size of the rest of the army) priests in one of their backwater cities and maybe a few longbowmen in their border cities even while in war. They occasionally move the stack between cities and might send some priest along with an attack force, but that's about it.